Weyl-Kondo semimetal: Extreme topological tunability and nonlinear optical exploration*

The recent surge of interest in exploring strongly correlated variants of topological semimetals has raised compelling questions about how to engineer, control, and detect their gapless topological nature. One amenable platform to map out this landscape is heavy fermion materials, which can harbor the theoretically established¹ and experimentally indicated² Weyl-Kondo semimetal (WKSM) phase, or a nodal line Kondo semimetal phase predicted based on the cooperation of strong correlations and space-group symmetry³. However unlike weakly correlated topology, where the chiral anomaly or electronic dispersion can be observed, wholly different experimental signatures of nontrivial topology are needed for strongly correlated systems. In the first part of this talk, I will show theoretical work on fine control of the Weyl-Kondo nodes under a relatively small Zeeman field through multiple topological phase transitions⁴, and survey the experiments on the WKSM candidate Ce₃Bi₄Pd₃ which indicate strongly correlated topology and its control by magnetic field⁵. Finally, owing to the high sensitivity of the WKSM, photoinduced phase transitions can be detected through emission spectra exhibiting high-harmonic generation, in addition to information about electronic structure and band topology. In the second part of the talk, I will present this recent work on nonlinear optical effects in the WKSM, towards an ultimate control of electronic topology on-demand.

¹H.-H. Lai, S. E. Grefe, S. Paschen, Q. Si, PNAS 115 1 2018 & PRB 101 075138 2020

²S. Dzsaber et al., PRL 118 246601 2017 & PNAS 118 8 2021

³L. Chen et al., 2021 arXiv:2107.10837; C. Cao, G.-X. Zhi, J.-X. Zhu, PRL 124 166403 2020

⁴S. E. Grefe, H.-H. Lai, S. Paschen, Q. Si, 2020 arXiv:2012.15841

⁵S. Dzsaber et al., 2019 arXiv:1906.01182